The quantum dot (QD) may also be called nanocrystalline, it is a nanoparticle consisting of II-VI family or III-V family elements, since electrons and holes are confined by quanta, successive energy band structures become discrete energy level structures having molecular properties, which can emit fluorescent light after being excitated, the luminescent spectrum thereof can be controlled by changing the size of the quantum dot, the fluorescent intensity and stability are both good, which is a perfect electroluminescent material. There is a great variety of quantum dots, which are represented by CdS, CdSe, CdTe, ZnO, ZnS, ZnSe, ZnTe of II-VI family and GaAs, GaP, GaAs, GaSb, HgS, HgSe, HgTe, InAs, InP, InSb, AlAs, AlP, AlSb of III-V family.
At present, the quantum dot as a display material has been widely used in the field of display, for example, quantum dot light emitting display (QLED) manufactured by using quantum dots as the luminescent material. The structure used by the existing QLED display is similar as the organic light emitting display (OLED), which controls the cathode of the QLED display device in the QLED display through the on-off action of the TFT, so as to control the QLED display device to emit light or not emit light, i.e., controlling flicker of the QLED display device. However, the QLED display of the prior art has the following problems: the existing QLED display controls the frequent flicker of the QLED display device through constant change of the driving current, hence, it may result in unbalance of injection of charges (i.e., the number of injected electrons and holes is unbalanced), repetition of this process for a long time may result in chemical dissociation of the quantum dots (e.g., oxidation/deoxidization) thereby property change may occur, such that the life time of the QLED display device is reduced; moreover, the way of controlling the cathode of the QLED display device in the QLED display through on-off action of the TFT to realize change of the driving current so as to control flicker of the QLED display device has the problem that the current control is unstable, which requires a complex compensation circuit to compensate the current, hence, the difficulty for preparation of the QLED display device of the prior art is great.